Drill chip breaker



y 1950 w. R. WIQHMAN 2,515,539

DRILL CHIP BREAKER Filed Jan. 10, 1948 INVENTOR.

William R, Wichman BY M MM ((1% Patented July 18, 1950 DRILL CHIP BREAKER William R. Wichman, Detroit, Mich., assignor to Ex-Cell-O Corporation, Detroit, Mich, a corporation of Michigan Application January 10, 1948, Serial No. 1,610

3 Claims. 1

The invention relates to drill chip breakers generally and more particularly to an improved chip breaker of the type adapted to be incorporated in the rotary drive for a drill, and operative to exert an axial thrust on the drill and to relieve it alternately during its rotation for the purpose of severing chip curls formed in the drilling operation.

One object of the invention is to provide improved means for eflecting periodic axial projection and retraction of the drill incident to its rotation in which the periodicity is out of synchronism with respect to such rotation, thereby eliminating any tendency of the drill to lead 011 to one side in the event that the cutting edges or lips thereof are not ground to identical form.

Another object is to provide an improved arrangement for driving the means utilized to effect alternate retraction and projection of the drill, whereby successive reciprocatory movements of the drill are spaced at intervals such as to insure breaking of the chip curls into lengths which are readily cleared from the hole by the flutes of the drill, and which permit a free flow of coolant along the flutes to the cutting edges of the drill.

Another object is to provide a drill chip breaker which is simple and rugged in construction, small in size, and characterized by low internal friction.

Other objects and advantages of the invention will become apparent'from the followingdetailed description of the preferred embodiment illustrated in the accompanying drawing, in

which:

Figure 1 is a longitudinal sectional view of a chip breaker embodying the features of the invention.

Fig. 2 is a transverse sectional view of the chip breaker taken in a horizontal plane substantially on the line 2--2 of Fig. 1. l I

Fig. 3 is an enlarged fragmentary sectional view taken in the same plane as Fig. 1. l 1

While the invention is susceptible of vario modifications and alternative constructions, I have shown in the drawing and'will herein describe in detail the preferred embodiment, but it is to be understood that I do not thereby intend to limit the invention to the specific form disclosed, but intend to cover all modifications and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

Referring more-particularly to the drawing, the drill chip breaker selected to illustrate the invention comprises a casing having a hollow cylindrical body section II with an inturned annular flange l2 at one end. A flanged cover section 13 is removably secured to the other end of the body as by screws I4 threaded into a spacing ring 15 which is rigidly secured to the body by screws I6. Extending through a central opening I! in the cover I3 is a rotary driving member l8 adapted to be connected with and supported from a spindle l9 constituting the tool supporting element of a machine tool. The driving member I8 is maintained in assembled relation with the casing In by a circumferential flange formed thereon and engaging in a recess 2| in the inner face of the cover member l3 concentric with the opening H. An arm 22 rigid with and projecting laterally from the cover section I3 is adapted tohold the casing stationary while the driving member 18 is being rotated.

Extending through the opening defined by the flange l2 of the body II is a driven member 25 adapted to support a rotary cutting tool, such as a drill 26, in axial relation. The outer or projecting end of the driven member 25 may be of any preferred construction, depending upon the manner in which the tool 26 is to be supported. As herein shown, the member is formed with a tapered socket 21 for receiving the complemental tapered shank of the tool 26. The driven member 25 is retained in assembled relation with the casing ill by an integral circumferential flange 28 adapted to seat against the inner face of the body flange 12.

To permit the drill to be axially projected and retracted during its rotation, the driving and driven members I8 and 25 are alined axially and are connected within the casing H) for rotation as a unit and for limited relative axial movement. More particularly, the driven member 25 is formed with a diametrical tank 30 having a cylindrical axial extension 3| which serves as a pilot for maintaining the members accurately alined. The adjacent end of the companion or driving member I8 is formed with a diametrical recess 32 complemental in cross section to the tank 30 and adapted to receive the same with a sliding fit. A bore 33 extends axially inwardly from the recess 32 to receive the pilot 31. In

is fed to the work. In the exemplary embodiment, the bearing structure includes a thrust plate 35 rigidly clamped in the casing between the spacing ring l5 and the cover [3. A central opening 36 in the plate accommodates the inner end of the driving member I8 and the thrust of the member is transmitted to the plate by suitable bearing elements, herein shown as balls 31, coacting with annular bearing races 38 and 39 formed respectively in the lower face of the flange and in the upper face of the plate 35.

Interposed between the lower face of the plate and a rotatably supported driving member or thrust ring is an antifriction bearing unit comprising a cage or bearing retainer 4! having a series of circumferentially spaced pockets for the accommodation of bearing elements 42, preferably ball bearings. The opposed faces of the bearing plate 35 and the thrust ring 4!] thus form stationary and rotating surfaces upon which the balls 42 roll when the ring is rotated, thus causing the retainer 4| to rotate at one-half the speed of the ring. To efiect retraction and projection of the member 25 relative to the member I8, one of the bearing surfaces, preferably the surface of the plate 35, is formed to provide an undulating track for the balls 42. The undulations are formed, in this instance, by shallow drop grooves 43 extending diametrically across the face of the plate.

In the exemplary embodiment, the retainer M is formed with six pockets for accommodating six of the balls a2. These pockets are non-uniformly spaced apart, as shown in Fig. 2, and the bearing face of the plate 35 is formed with three of the drop grooves 43 spaced apart angularly so that the portions on opposite sides of the axis of the plate are located similarly to the pockets. Ac-

cordingly, all of the balls :32 will register with the grooves simultaneously only when the retainer 4! occupies certain definite positions with respect to" the plate 35 namely, the positions in which the pockets and the grooves are in registration. In all other positions of the retainer, the balls will ride up on the bearing surface of the plate 35 and hold the driven member 25 in projected relation to the driving member i8. As the retainer in its rotation carries the balls 42 into registration with the grooves 13, the balls drop into the same and allow the driven member to retract or move inwardly toward the driving member. When this occurs during the advance of the spindle 19, the feeding movement of the drill 25 is interrupted or substantially decreased, thus introducing a momentary dwell in the cutting action of the tool. In the continued rotation of the retainer, the balls 42 climb out of the grooves and project the driven member and the drill axially away from the driving member back into normal cutting position. This alternate retraction and projection of the drill serves to sever or break the chip curl out from the work.

In accordance withthe present invention, novel means is incorporated in the bearing structure for rotatably driving the thrust ring 46 from the member 25 but at a substantially slower speed and out of synchronism therewith. The reciprocations of the drill are therefore non-synchronous with respect to its rotation which faciiltates the grinding of the cutting edges or lips of the drill to produce a balanced cut and effectually eliminates any tendency of the drill to lead off to one side. The drive, as herein shown, is effected through a series of balls 45 of uniform diameter interposed between the inner face of the flange 28 and the ring 40, the balls being retained in a cage 46 which is nonrotatably secured in the casing ID. The rotation of the driven member 25 is therefore operative through the frictional engagement between the balls and the flange 28 to rotate each ball individually about a horizontal axis 41 passing through the center of the ball, as indicated diagrammatically in Fig. 3. Since the coacting surfaces of the flange and the balls are smooth, some slippage necessarily occurs which prevents the balls from rotating in synchronism with the driven member.

To obtain the desired speed reduction, the ring 40 is formed with an annular bearing track in the form of a groove 50 having inwardly sloping side walls 5| and 52. By forming the groove 50 with a depth somewhat greater and a width slightly less than the diameter of the individual balls 45, the walls 5| and 52 are enabled to serve as bearing surfaces for the balls. Since these bearing surfaces are at the sides rather than at the base of the groove, the points'of contactA between the walls 5[ and 52 and each ball are closer to the axis 4"! of the ball than the, point of contact B between the flange 28 and the ball; The ring 40 is therefore rotated. opposite to the direction of rotation of the driven member, and at a speed which is equal to the rotative speed of the driven member times'the ratio OC/OB, where 0C represents the-distance from the center of the ball to a plane passing through the contact points A, and 013 the distance from the center of the ball to the contact point B. a V

In the particular structure illustrated, the groove 31 is dimensioned so that the ratio of O0 to OB is 1:3. Disregarding slippage, the ring li] therefore makes'one revolution for each-three revolutions of themember 25. Accordingly, since the drill is retracted and projected once in each revolution of the ring-40' due to the spacing of the drop grooves flasexplained heretofore, the projection and retraction as compared to drill rotation is effected at relatively widely spaced intervals as, for example, once for each three revolutions of the drill. This allows the formation of chips of a length that canbe readily cleared from the hole by the flutes of the drilland that define interstices in the masswhich permit the coolant to flow freely along the flutes to the cutting edges of the drill. i

As indicated heretofore, some slippage is inherent in a friction drive of the type above de* scribed and the amount of such slippage is somewhat indeterminate. With the construction illustrated, the slippage effectually preventsthe ring 40 from rotating in synchronism with the driven member 25 and consequently the reciprocations of the drill are not effected in absolute synchronism with its rotation. I The drill is therefore enabled to produce a straight hole even though the cutting edges are not ground to identical form. r A

It will be apparent from-the foregoing that th invention provides a drill chip breaker of novel 1 and advantageous construction. Through a novel arrangement of antifriction bearings the drill is momentarily relieved and projected axial- 1y during its rotation, thus enabling it to effectually sever the chip curls removed from the work. By the action of the novel drive means incorporated in the bearing structure, the reciprocations of the drill are timed so as to insure formation of chips which can be readily cleared from the hole by the flutes of the drill. Moreover, while the reciprocations of the drill- 5 are effected as an incident to its rotation, they are not synchronous with such rotation, thereby eliminating any tendency of the drill to lead off to one side in case the cutting edges or lips are not ground to identical form. The improved chip breaker is simple and rugged in construction and, since the chip breaking movements are efiected through the medium of antifriction bearings, it is characterized by very low internal friction.

I claim as my invention:

1. A drill chip breaker comprising, in combina-- tion, a rotatable drill supporting member, means for imparting an axial thrust to said member including a nonrotatable thrust plate having one face formed to provide an undulating bearing track generally perpendicular to the axis of said member, a thrust ring mounted in opposed relation to said plate and having its adjacent face formed to provide a plane bearing track, antifriction bearing elements interposed between said plate and said ring for coaetion with said tracks, means for rotatably driving said ring from said member and at a reduced speed including a series of balls interposed between an annular bearing track on said member and the adjacent face of said ring, said face having formed therein an annular groove with inclined side walls forming tracks for said balls engageable therewith at points closer to the rotational axis of the balls than the points of engagement between said balls and said annular bearing track.

2. In a drill chip breaker, in combination, driving and driven members supported in axial relation and interconnected for rotation as a unit and for relative axial movement, means for periodically retracting and projecting said driven member with respect to said driving member including a nonrotatable thrust element and a rotatable balls of uniform diameter interposed between said rotatable thrust element and an opposed plane bearing surface formed on said driven member, said rotatable thrust element being formed with an annular groove having inclined side walls spaced apart to engage each of said balls at points closer to the rotational axis of the ball than the point of contact of said plane bearing surface with the ball.

3. In a drill chip breaker, in combination, driving and driven members supported in axial relation and interconnected for rotation as a unit and for relative axial movement, means for periodically retracting and projecting said driven member with respect to said driving member including a nonrotatable thrust element and a rotatable thrust element mounted in opposed relation, antifriction bearing elements interposed between said thrust elements, one of said thrust elements having its bearing engaging face formed to provide an undulating track for said bearing elements, means for rotatably driving said rotatable thrust element from said driven member but at a slower speed comprising a series of balls of uniform diameter interposed between said rotatable thrust element and an opposed plane bearing surface formed on said driven member, a retainer for said balls secured against rotation with the driven member and operative to restrict the balls to rotation about their individual axes, said rotatable thrust element being formed with an annular groove having inclined side walls constituting bearing tracks for said balls and spaced apart to engage each ball at points whose spacing from the rotational axis of the ball is less than the radius of the ball.

WILLIAM R. WICHMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,196,656 Bugbee Aug. 29, 1916 1,523,629 Bullock Jan. 20, 1925 1,528,530 Coffee Mar. 3, 1925 2,430,019 Jenkins Nov. 4, 1947 

